Production of copolymers by way of emulsion polymerization

Abstract

The invention relates to methods for producing copolymers in the form of aqueous dispersions or of powders that can be redispersed in water, by radical-initiated emulsion polymerization of one or more ethylenically monounsaturated monomers and one or more ethylenically polyunsaturated monomers (cross-linking monomers) and optional subsequent drying, characterized in that ≥ 85 wt.% of the ethylenically monounsaturated monomers are polymerized and then one or more ethylenically polyunsaturated monomers are added, the percentage by weight indication relating to the total weight of the ethylenically monounsaturated monomers.

Description

[0001] Production of copolymers by emulsion polymerization

[0002] The invention relates to processes for the preparation of copolymers by emulsion polymerization of monoethylenically unsaturated monomers and polyethylenically unsaturated monomers, the copolymers obtainable thereby in the form of aqueous dispersions or water-redispersible powders and their use in coating compositions or adhesives.

[0003] For the application of polymers based on ethylenically unsaturated monomers, their film properties are a key characteristic. The film properties are determined on the one hand by the monomers and on the other hand by the molecular weights, glass transition temperatures (Tg) and minimum film formation temperatures (MFT) of the polymers. The film properties, such as the homogeneity of the polymer films, can also be influenced with additives. Very different requirements are placed on polymers depending on the area of ​​application. For example, for some coating applications, such as wall paints, copolymers with low minimum film formation temperatures are required for processability over a broad temperature range, whereas polymers with high glass transition temperatures are used for scratch-resistant and non-tacky surface coatings.In adhesive applications, such as bonding paper or other substrates, the adhesion / cohesion balance is particularly important. Until now, it was necessary to develop a separate polymerization process for each polymer with its characteristic property profile, using a specific selection of monomer combinations and special polymerization schemes.

[0004] One known method for adjusting the adhesion / cohesion ratio of polymer films or improving their mechanical properties, such as tensile strength or elongation properties, is the copolymerization of crosslinker monomers to obtain polymers with a specific degree of crosslinking. Crosslinker monomers are generally referred to as polyethylenically unsaturated monomers, such as (meth)acrylic acid esters with additional allyl or vinyl groups. Unfortunately, the copolymerization of crosslinker monomers in emulsion polymerization processes also regularly has a significant impact on the other property profile of the polymerization products, such as the average particle size or particle size distribution of the copolymers. This applies particularly to polymerizations with vinyl ester monomers.This problem has so far been addressed by developing, for example, complex, tailor-made dosing processes or multi-stage polymerization processes for each individual case in order to obtain copolymers with the overall desired property profile for the respective monomer combination or the respective application.

[0005] Multi-stage emulsion polymerization processes are known in which the crosslinking monomers are usually polymerized in a first stage, thus forming core-shell copolymers. For example, J. Garrett, P.A. Lovell, A.J. Shea, and R.D. Viney show in Macromol. Symp. 151, pages 487-496 (2000) that core-shell copolymers with a crosslinked core based on the "hard" methyl methacrylate (MMA) and allyl methacrylate (ALMA) improve the peel adhesion of water-based pure acrylic pressure-sensitive adhesives (PSAs). The core-shell copolymers were prepared by dosing MMA and ALMA in a first stage and dosing under "straved conditions" in a second step.Also known in the field of pressure-sensitive adhesives is the use of crosslinkers such as allyl methacrylate in conjunction with chain transfer agents (CTAs) to influence the polymer microstructure of multi-stage emulsion polymers. For example, in "Manipulating Latex Polymer Microstructure Using Chain Transfer Agent and Cross-Linker to Modify PSA Performance and Viscoelasticity. Macromolecular Reaction Engineering," 5: pages 117-128, doi: 10.1002 / mren.201000046, Qie, L. and Dube, M.A. (2011) describe the ALMA used as a crosslinker being dosed together with the majority of monomers to form an in-situ BA / MMA seed polymer. The study shows that by varying the CTA content without using the crosslinker, higher weight-average molecular weights (Mw) and higher average molecular weights between crosslinking points (M. C) and correspondingly higher shear strengths can be achieved than with combinations of both components. In another study on two-stage interpenetrating polymer networks, allyl methacrylate was used to adjust the degree of crosslinking of a first copolymer. The first polymer is a polymer of n-butyl acrylate, styrene, acrylic acid and the crosslinking monomer allyl methacrylate. A second polymer phase consisted of styrene and butadiene in varying compositions. All two-stage copolymers were carried out as semi-continuous emulsion polymerization at approximately 90°C. To improve the low-temperature stability of coatings for upholstered furniture, H. Warson and CAFinch in Applications of Synthetic Resin Latices, Volume 3, Latices in Diverse Applications, ISBN: 978-0-471-95462-0, 2001, page 1525, describes the copolymerization of allyl methacrylate (ALMA) as a crosslinker with butyl acrylate (BA), itaconic acid (ITA), methacrylamide (MA), and methyl methacrylate (MMA) in a weight ratio of 1:86:1:7.5:5. US4973670 discloses a multi-stage production process for hollow polymer particles in which the crosslinker monomer allyl methacrylate is added as part of a second monomer batch to a prepolymerized but only partially polymerized first monomer batch. GB2206591A teaches core / shell / shell copolymers whose shell is based on several unsaturated monomers including allyl methacrylate. Lee and Rudin have in Makromol.

[0006] Chem. Rapid Commun. 10, page 655 (1989) ) five weight percent allyl methacrylate is polymerized into the core of core / shell latex particles to obtain a core gel fraction.

[0007] Ethylenically unsaturated polymers are also obtainable by emulsion polymerization processes with polyethylenically unsaturated comonomers, such as allyl methacrylate (ALMA), by controlling the proportion of free allyl groups in the copolymer, for example, by special dosing strategies, as described by JW Taylor, MA Winnik in JCT Research, Vol. 1, No. 3 July 2004, pages 163-191 for styrene acrylates with ALMA as comonomer. US3660537 teaches the polymerization of allyl methacrylate into graft copolymers of MMA, diethylaminoethyl methacrylate (DEAM) and optionally 2-ethylhexyl acrylate (2-EHA) and n-butyl acrylate (BA) for coating compositions, with the aim of introducing ethylenically unsaturated allyl groups which are freely polymerizable by allyl methacrylate into the graft copolymers.US3219610 describes the use of allyl methacrylate for the production of unsaturated (meth)acrylate emulsion polymers and their use in coating compositions. The polymers were produced using a batch process; the proportion of free allyl groups in the polymer was not determined. US5783626 describes the use of allyl methacrylate for introducing free allyl groups into multi-stage emulsion polymers, which were subsequently further modified with propyleneimine and acetoacetoxy-functional monomers. Allyl methacrylate was added together with other monomers to a first emulsion polymer stage containing a crosslinker. Finally, US5264482 teaches the polymer-analogous reaction of carboxylic acid-containing copolymers with allyl glycidyl ether for the production of water-soluble copolymers as a curing additive for latex paints.

[0008] However, such approaches are characterized by multi-stage polymerizations with complex dosing strategies, which have to be adapted to the desired property profile for the respective polymer application through complex development work, which then results in complexity and effort in the commercial production of the most diverse copolymers using a wide variety of processes.

[0009] In the production of vinyl ester or vinyl ester-ethylene copolymer dispersions, copolymerization under conventional initial charging and metering of crosslinking monomers results in copolymers with massively broadened particle size distributions, which has a disadvantageous effect on the use of such copolymers, for example in paint applications.

[0010] Against this background, the task was to provide measures with which the tensile strength and / or advantageous adhesion / cohesion balance of polymer films can be influenced using established polymerization processes with technically simple measures involving copolymerization of crosslinking monomers, if possible without significantly interfering with the particle size distribution or the average particle sizes of the copolymers. This goal was to be achieved, if possible, for copolymers with different property profiles using the same solution approach. Such problems should be solved particularly preferably for vinyl ester copolymers.

[0011] The invention relates to processes for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders by free-radical initiated emulsion polymerization of one or more monoethylenically unsaturated monomers and one or more polyethylenically unsaturated monomers (crosslinker monomers) and optionally subsequent drying, characterized in that > ​​85 wt . % of the monoethylenically unsaturated monomers are polymerized and then one or more polyethylenically unsaturated monomers are added, the data in wt . % relating to the total weight of the monoethylenically unsaturated monomers.

[0012] The invention further relates to copolymers in the form of aqueous dispersions or water-redispersible powders obtainable by the aforementioned radically initiated emulsion polymerization process.

[0013] The term monomers includes the monoethylenically unsaturated monomers and the crosslinker monomers. The total weight of the monomers generally includes the weight of the total monomers used in the process. The total weight of the monoethylenically unsaturated monomers generally includes the weight of the total monoethylenically unsaturated monomers used in the process. The total weight of the crosslinker monomers generally includes the weight of the total crosslinker monomers used in the process.

[0014] The polyethylenically unsaturated monomers (crosslinking monomers) preferably carry 2 to 6, particularly preferably 2 or 3 and most preferably 2 ethylenically unsaturated groups.

[0015] In addition to the ethylenically unsaturated groups, preferred crosslinking monomers preferably carry at least one or more further functional groups, in particular ester, amide, ether, carbonate, cyanurate, or thioether groups. Preferred further functional groups are ester, amide, and ether groups.

[0016] Particularly preferred are vinyl or allyl esters of ethylenically unsaturated carboxylic acids, in particular vinyl (meth)acrylates or allyl (meth)acrylates; di(meth)acrylate compounds; tri-(meth)acrylate compounds; bis-(meth)acrylamide compounds; di- or triallyl compounds, such as diallyl esters of saturated or ethylenically unsaturated dicarboxylic acids or triallyl esters of saturated or ethylenically unsaturated tricarboxylic acids; di- or trivinyl compounds, such as divinyl esters of saturated or ethylenically unsaturated dicarboxylic acids or trivinyl esters of saturated or ethylenically unsaturated tricarboxylic acids; divinyl or triallyl aromatics; divinyl or triallyl ethers; or divinyl or diallyl carbonate.

[0017] Beispiele für Vernetzermonomere sind Allylmethacrylat , Allylac- rylat , Vinylmethacrylat , Vinylacrylat , Diethylenglycoldimethac- rylat , Triethylenglykoldimethacrylat , Ethylenglykoldiacrylat , 1 , 3-Butylenglykoldiacrylat , Propylenglykoldiacrylat , 1 , 3-Gly- cerindimethacrylat , 1 , 1 , 1-Trimethylolethandiacrylat , 1 , 1 , 1- Trimethylpropandimethacrylat , Methylenbisacrylamid, Methylen- bismethacrylamid, Diallylmaleat , Diallyl fumarat , Diallylitaco- nat , Diallylmalonat , Diallylphthalat , Vinylcrotonat , Divinyla- dipat, Divinylbenzol, Divinylether, Ethylenglykoldivinylether, Diallylcarbonat, Trimethylolpropan-trimethacrylat , Pentaeryth- rittrimethacrylat , Triallylcyanurat (TAG) , Triallylisocyanurat , Triallylcitrat, Triallylaconitat oder Sorbitol-Pentamethacry- lat .

[0018] Preferred examples of crosslinker monomers are allyl methacrylate, allyl acrylate, triethylene glycol dimethacrylate, ethylene glycol diacrylate, methylenebisacrylamide, diallyl maleate, diallyl fumarate, diallyl itaconate, triallyl cyanurate (TAG), or triallyl isocyanurate. Particular preference is given to allyl methacrylate, methylenebisacrylamide, diallyl fumarate, or triallyl cyanurate (TAG).

[0019] The crosslinking monomers are used in an amount of preferably 0.01 to 5 wt.%, particularly preferably 0.1 to 2.5 wt.% and most preferably 0.2 to 1 wt.%, based on the total weight of the monomers.

[0020] The crosslinking monomers are used in an amount of preferably 0.01 to 5 wt.%, particularly preferably 0.1 to 2.5 wt.% and most preferably 0.2 to 1 wt.%, based on the total weight of the monoethylenically unsaturated monomers.

[0021] >85 wt.%, preferably >90 wt.%, particularly preferably >93 wt.%, and most preferably >95 wt.% of the monoethylenically unsaturated monomers are polymerized, and then one or more crosslinker monomers are added, based on the total weight of the monoethylenically unsaturated monomers. This information generally refers to the initial addition of crosslinker monomers.

[0022] Preferably, the gravimetric conversion of the monoethylenically unsaturated monomers at the time at which the addition of the crosslinker monomers begins is preferably > 85 wt. %, more preferably > 90 wt. % and most preferably > 93 wt. %. Preferably, < 99 wt. %, more preferably < 98 wt. % and most preferably < 97 wt. % of the monoethylenically unsaturated monomers are polymerized and then one or more crosslinker monomers are added. These data in wt. % relate to the total weight of the monoethylenically unsaturated monomers. The conversion generally relates to the initial addition of crosslinker monomers. This gravimetric conversion is determined as the quotient of the actual solids content of a dispersion and the theoretically possible solids content of the dispersion upon complete polymerization of the monomers present in the reaction mixture.The actual solids content is determined gravimetrically by weighing 0.3 g of copolymer dispersion and drying it as a thin film for 30 minutes at 110°C in a circulating air drying cabinet. The drying residue is cooled in a desiccator over silica gel, then reweighed, and the solids content in wt. %, based on the dispersion, is calculated from the residue and the initial weight. The theoretically possible solids content is calculated from the components with a boiling point of > 110°C at 1 bar.

[0023] Preferably, the crosslinker monomers are added at > 70 wt.%, more preferably > 85 wt.%, even more preferably > 95 wt.%, and most preferably > 98 wt.%, based on the total weight of the crosslinker monomers, at a time when the monoethylenically unsaturated monomers have polymerized to > 85 wt.%, in particular > 95 wt.%, based on the total weight of the monoethylenically unsaturated monomers. Most preferably, the total amount of crosslinker monomers used is added at a time when the monoethylenically unsaturated monomers have polymerized to > 85 wt.%, in particular > 95 wt.%, based on the total weight of the monoethylenically unsaturated monomers.

[0024] The monoethylenically unsaturated monomers are used in an amount of preferably 95 to 99.99 wt.%, particularly preferably 97.5 to 99.9 wt.%, and most preferably 99 to 99.8 wt.%, based on the total weight of the monomers. Monoethylenically unsaturated monomers can be selected, for example, from the group comprising vinyl esters, (meth)acrylic acid esters, vinyl aromatics, olefins, and vinyl halides.

[0025] Suitable vinyl esters are, for example, those of carboxylic acids having 1 to 15 C atoms. Preference is given to vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl pivalate and vinyl esters of «-branched monocarboxylic acids having 9 to 11 C atoms, such as VeoVa9 R or VeoVal O R (Trade names of Resolution). Vinyl acetate is particularly preferred.

[0026] Suitable monomers from the group of acrylic acid esters or methacrylic acid esters are, for example, esters of unbranched or branched alcohols having 1 to 15 carbon atoms. Preferred methacrylic acid esters or acrylic acid esters are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, and 2-ethylhexyl acrylate. Methyl acrylate, methyl methacrylate, n-butyl acrylate, t-butyl acrylate, and 2-ethylhexyl acrylate are particularly preferred.

[0027] Preferred vinylaromatics are styrene, methylstyrene, and vinyltoluene. The preferred vinyl halide is vinyl chloride. The preferred olefins are ethylene and propylene.

[0028] If desired, from 0 to 20% by weight, in particular from 0.1 to 10% by weight, based on the total weight of the monomers, of auxiliary monomers can be copolymerized as monoethylenically unsaturated monomers. Examples of auxiliary monomers are ethylenically unsaturated mono- and dicarboxylic acids, preferably acrylic acid, methacrylic acid, fumaric acid and maleic acid; ethylenically unsaturated carboxamides and nitriles, preferably acrylamide and acrylonitrile; mono- and diesters of fumaric acid and maleic acid, such as the diethyl and diisopropyl esters and also maleic anhydride; ethylenically unsaturated sulfonic acids or their salts, preferably vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid.Further examples are post-crosslinking comonomers, for example acrylamidoglycolic acid (AGA), methylacrylamidoglycolic acid methyl ester (MAGME), N-methylolacrylamide (NMA), N-methylolmethacrylamide, N-methylolallylcarbamate, alkyl ethers such as isobutoxy ether or esters of N-methylolacrylamide, N-methylolmethacrylamide and N-methylolallylcarbamate. Epoxy-functional comonomers such as glycidyl methacrylate and glycidyl acrylate are also suitable. Further examples are silicon-functional comonomers such as acryloxypropyltri(alkoxy)- and methacryloxypropyltri(alkoxy)-silanes, vinyltrialkoxysilanes and vinylmethyldialkoxysilanes, where ethoxy and ethoxypropylene glycol ether residues, for example, can be present as alkoxy groups.Monomers with hydroxy or CO groups may also be mentioned, for example methacrylic acid and acrylic acid hydroxyalkyl esters such as hydroxyethyl, hydroxypropyl or hydroxybutyl acrylate or methacrylate as well as compounds such as diacetone acrylamide and acetylacetoxyethyl acrylate or methacrylate.

[0029] The monomer selection or the selection of the weight fractions of the comonomers is carried out such that a glass transition temperature Tg of preferably -50°C to +50°C, more preferably -30°C to +40°C and particularly preferably -20°C to +20°C results. The glass transition temperature Tg of the polymers can be determined in a known manner by means of differential scanning calorimetry (DSC). The Tg can also be approximately predicted using the Fox equation. According to Fox TG, Bull. Am. Physics Soc. 1, 3, page 123 (1956), the following applies: 1 / Tg = xl / Tgl + x2 / Tg2 + ... + xn / Tgn, where xn is the mass fraction (wt. % / 100) of the monomer n, and Tgn is the glass transition temperature in Kelvin of the homopolymer of the monomer n. Tg values ​​for homopolymers are listed in Polymer Handbook 2nd Edition, J. Wiley & Sons, New York (1975).

[0030] Preference is given to copolymers of vinyl acetate with 1 to 50% by weight of ethylene; copolymers of vinyl acetate with 1 to 50% by weight of ethylene and 1 to 50% by weight of one or more further comonomers from the group consisting of vinyl esters having 1 to 12 carbon atoms in the carboxylic acid radical, such as vinyl propionate, vinyl laurate, vinyl esters of alpha-branched carboxylic acids having 9 to 13 carbon atoms, such as VeoVa9, VeoValO, VeoVall; copolymers of vinyl acetate, 1 to 50% by weight of ethylene and preferably 1 to 60% by weight of (meth)acrylic esters of unbranched or branched alcohols having 1 to 15 carbon atoms, in particular n-butyl acrylate or 2-ethylhexyl acrylate; and copolymers with 30 to 75% by weight of vinyl acetate, 1 to 30% by weight of vinyl laurate or vinyl ester of an alpha-branched carboxylic acid having 9 to 11 C atoms, and 1 to 30% by weight of (meth)acrylic acid esters of unbranched or branched alcohols having 1 to 15 C atoms, in particular n-butyl acrylate or 2-ethylhexyl acrylate, which also contain 1 to 40% by weight.-% ethylene; copolymers with vinyl acetate, 1 to 50 wt.% ethylene and 1 to 60 wt.% vinyl chloride; where the copolymers also contain 0.01 to 5 wt.%, preferably 0.1 to 2.5 wt.% and most preferably 0.2 to 1 wt.% crosslinking monomers; and where the copolymers can also contain the said auxiliary monomers in the stated amounts, and the data in wt.% add up to 100 wt.% in each case.

[0031] Also preferred are (meth)acrylic acid ester polymers, such as copolymers of n-butyl acrylate or 2-ethylhexyl acrylate or copolymers of methyl methacrylate with n-butyl acrylate and / or 2-ethylhexyl acrylate; styrene-acrylic acid ester copolymers with one or more monomers from the group methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate; vinyl acetate-acrylic acid ester copolymers with one or more monomers from the group methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate and optionally ethylene; styrene-1,3-butadiene copolymers; wherein the copolymers also contain 0.01 to 5% by weight, preferably 0.1 to 2.5% by weight, and most preferably 0.2 to 1% by weight, of crosslinking monomers; and wherein the copolymers may also contain the said auxiliary monomers in the stated amounts, and the data in wt.% add up to 100 wt.% in each case.

[0032] Most preferred are copolymers with vinyl acetate and 5 to 50% by weight of ethylene, or copolymers with vinyl acetate, 1 to 50% by weight of ethylene and 1 to 50% by weight of a vinyl ester of α-branched monocarboxylic acids having 9 to 11 C atoms, or copolymers with 30 to 75% by weight of vinyl acetate, 1 to 30% by weight of vinyl laurate or vinyl ester of an alpha-branched carboxylic acid having 9 to 11 C atoms, and 1 to 30% by weight of (meth)acrylic acid esters of unbranched or branched alcohols having 1 to 15 C atoms, which also contain 1 to 40% by weight of ethylene, or copolymers with vinyl acetate, 5 to 50% by weight of ethylene and 1 to 60% by weight of vinyl chloride; wherein the copolymers also contain 0.01 to 5 wt.%, preferably 0.1 to 2.5 wt.% and most preferably 0.2 to 1 wt.% of crosslinking monomers.

[0033] The process according to the invention yields copolymers with conventional particle sizes, particle size distributions, and viscosities. Surprisingly and advantageously, the process according to the invention makes it possible to obtain copolymers into which crosslinker monomers are polymerized, yet which have essentially the same or comparable particle sizes, particle size distributions, and / or viscosities as corresponding or similarly prepared copolymers without crosslinker monomers. This is expressed by the following particle size and viscosity invariance parameters.

[0034] The particle size invariance of the copolymers produced according to the invention is preferably <30%, particularly preferably <25%, and most preferably <20%. Particle size invariance is the absolute value of the quotient of the particle size of a copolymer according to the invention and the particle size of a reference polymer minus 1 in percent. The reference polymer is produced identically to the copolymer according to the invention, with the sole difference that no crosslinking monomer is polymerized into the reference polymer. The particle size is determined using a Beckmann Coulter® LS 13320 measuring device according to the device instructions. The volume-weighted mean size is expressed in MV notation according to DIN ISO 9276-2.

[0035] The viscosity invariance of the inventively produced

[0036] Copolymers are preferably < 50%, particularly preferably < 30% and most preferably < 20%. The viscosity invariance is the absolute value of the quotient of the viscosity of a copolymer according to the invention and the viscosity of a reference polymer minus 1 in percent, where the reference polymer is prepared identically to the copolymer according to the invention, with the only difference being that no crosslinking monomer is polymerized into the reference polymer. The viscosity is determined using a Brookfield viscometer at 23°C at 20 rpm with a dispersion solids content of 55%.

[0037] The copolymers according to the invention preferably contain no or essentially no ethylenically unsaturated group (determination method: NMR).

[0038] The excess factor of the degree of crosslinking of the copolymers prepared according to the invention is preferably >1.1, particularly preferably >1.2 and most preferably >1.5. The excess factor of the degree of crosslinking is the quotient of the degree of crosslinking of a copolymer according to the invention and that of a reference polymer, the reference polymer being prepared identically to the copolymer according to the invention, with the only difference that no crosslinker monomer is polymerized into the reference polymer. The degree of crosslinking is determined by extracting soluble copolymer fractions with 90 mL ethyl acetate in a Soxhlet extractor (SQXTEC8000, FOSS GmbH) under reflux for 6 hours. The degree of crosslinking is the mass fraction of insoluble copolymer based on the initial weight of copolymer.

[0039] The copolymers are preferably stabilized with an emulsifier and / or protective colloid. The radically initiated emulsion polymerization preferably takes place in the presence of one or more emulsifiers and / or one or more protective colloids.

[0040] The copolymers are prepared by the emulsion polymerization process. The polymerization temperature is generally between 40 °C and 100 °C, preferably between 60 °C and 95 °C. When copolymerizing gaseous comonomers such as ethylene, 1,3-butadiene, or vinyl chloride, the process can also be carried out under pressure, generally between 5 bar and 100 bar.

[0041] Emulsion polymerization is typically carried out in an aqueous medium. Polymerization is preferably carried out in the absence of organic solvents such as alcohols, ethers, esters, aliphatic, or aromatic hydrocarbons.

[0042] The polymerization can be initiated using the redox initiator combinations commonly used for emulsion polymerization. The monomer conversion can be controlled, as usual, by adjusting the initiator dosage. The initiators are generally added in such a way as to ensure continuous polymerization. Examples of suitable oxidation initiators are the sodium, potassium, and ammonium salts of peroxodisulfuric acid, hydrogen peroxide, t-butyl peroxide, t-butyl hydroperoxide, potassium peroxodiphosphate, tert-butyl peroxopivalate, cumene hydroperoxide, and azobisisobutyronitrile. Preference is given to the sodium, potassium, and ammonium salts of peroxodisulfuric acid and hydrogen peroxide. The initiators mentioned are generally used in an amount of 0.01 to 2.0% by weight, based on the total weight of the monomers.

[0043] Suitable reducing agents include, for example, the sulfites and bisulfites of alkali metals and ammonium, such as sodium sulfite, and the derivatives of sulfoxylic acid, such as zinc or alkali formaldehyde sulfoxylates, for example sodium hydroxymethanesulfinate (Brüggolit), tartaric acid, and (iso-)ascorbic acid. Sodium hydroxymethanesulfinate, tartaric acid, and (iso-)ascorbic acid are preferred. The amount of reducing agent is preferably 0.015 to 3% by weight, based on the total weight of the monomers.

[0044] The oxidizing agents mentioned, in particular the salts of peroxodisulfuric acid and hydrogen peroxide, can also be used alone as thermal initiators. Regulators can be used to control the molecular weight during the emulsion polymerization process. If regulators are used, they are usually employed in amounts between 0.001 and 5.0 wt. %, based on the monomers to be polymerized, and are metered separately or premixed with the reaction components. Examples of such substances are n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptopropionic acids or their alkali metal salts, methyl mercaptopropionate, isopropanol, phosphonic acid or its derivatives, phosphinic acid or its derivatives, and acetaldehyde. 2-Mercaptopropionic acid or tert-dodecyl mercaptan is preferably used.

[0045] Protective colloids, preferably in combination with emulsifiers, can be used for stabilization. The polymers thus obtained are preferably in the form of protective colloid-stabilized, aqueous dispersions.

[0046] Examples of protective colloids are polyvinyl alcohols; polyvinyl acetals; polyvinylpyrrolidones; polysaccharides in water-soluble form such as starches (amylose and amylopectin), celluloses and their carboxymethyl, methyl, hydroxyethyl, hydroxypropyl derivatives, dextrins and cyclodextrins; proteins such as casein or caseinate, soy protein, gelatin; ligninsulfonates; synthetic polymers such as poly(meth)acrylic acid, copolymers of (meth)acrylates with carboxyl-functional comonomer units, poly(meth)acrylamide, polyvinylsulfonic acids and their water-soluble copolymers; melamine-formaldehydesulfonates, naphthalene-formaldehydesulfonates, styrene-maleic acid and vinylether-maleic acid copolymers.

[0047] Partially saponified or fully saponified polyvinyl alcohols with a degree of hydrolysis of preferably 80 to 100 mol% are preferred. Partially saponified polyvinyl alcohols with a degree of hydrolysis of 80 to 95 mol% are particularly preferred, in particular with a Höppler viscosity in 4% aqueous solution of 1 to 30 mPas (Höppler method at 20°C, DIN 53015). Most preferred are polyvinyl alcohols with a degree of hydrolysis of 85 to 94 mol%, in particular with a Höppler viscosity in 4% aqueous solution of 3 to 15 mPas (Höppler method at 20°C, DIN 53015). The protective colloids mentioned are accessible by means of processes known to the person skilled in the art.

[0048] The aqueous dispersions contain the protective colloids in an amount of preferably 1 to 20 wt . -% , based on the total weight of the copolymers .

[0049] In the emulsion polymerization process, polymerization can also be carried out in the presence of emulsifiers, such as anionic, cationic, or nonionic emulsifiers. Preferred amounts of emulsifiers are 1 to 7 wt.%, based on the total weight of the monomers.

[0050] Examples of anionic emulsifiers are alkyl sulfates with a chain length of 8 to 18 carbon atoms, alkyl or alkylaryl ether sulfates with 8 to 18 carbon atoms in the hydrophobic radical and up to 40 ethylene or propylene oxide units, alkyl or alkylaryl sulfonates with 8 to 18 carbon atoms, esters and half-esters of sulfosuccinic acid with monohydric alcohols or alkylphenols. Alkyl sulfonates and alkyl sulfates, especially lauryl sulfates, are particularly preferred.

[0051] Examples of non-ionic emulsifiers are those with alkylene oxide groups, in particular acyl, alkyl, oleyl or alkylaryl ethoxylates, such as alkyl polyglycol ethers or alkylaryl polyglycol ethers with 8 to 40 ethylene oxide units. Preference is given to ethoxylated mono-, di- and trialkylphenols (preferably with an EO degree of 3 to 50 and an alkyl substituent radical from C4 to C12) and ethoxylated fatty alcohols (preferably with an EO degree of 3 to 80 and an alkyl radical from Cs to Cse), in particular C10-C14 fatty alcohol (3-40) ethoxylates, polyoxyethylene sorbitan monooleate with 20 ethylene oxide groups, copolymers of ethylene oxide and propylene oxide with a minimum ethylene oxide content of 10 percent by weight, the polyethylene oxide (4-40) ethers of oleyl alcohol and the polyethene oxide (4-40) ethers of nonylphenol. Particularly preferred are the polyethylene oxide (4-40) ethers of fatty alcohols, in particular of oleyl alcohol, stearyl alcohol or Cn-alkyl alcohols.

[0052] The emulsion polymerization can be carried out in conventional polymerization reactors, for example in pressure reactors and / or pressureless reactors. Conventional, appropriately dimensioned steel reactors with stirring devices, heating / cooling systems and lines for supplying the reactants and removing the products can be used as pressure reactors or pressureless reactors. When using gaseous monomers, such as ethylene, a pressure reactor and, if appropriate, an additional pressureless reactor are preferably used. The preferred working pressure in the pressure reactor is 3 to 120 bar, particularly preferably 10 to 80 bar. The preferred working pressure in the pressureless reactor is 100 mbar to 5 bar, particularly preferably 200 mbar to 1 bar.

[0053] The emulsion polymerization is preferably carried out in batch or semi-batch processes, but can also be carried out in a continuous process, with the proviso that the crosslinking monomers are added according to the invention.

[0054] In a batch or semi-batch process, the monoethylenically unsaturated monomers can, for example, be introduced in their entirety, added in their entirety, or partially introduced and the remainder metered in. The preferred procedure is that the monoethylenically unsaturated monomers are introduced in an amount of 20 to 100% by weight, in particular 30 to 60% by weight, based on the total weight of the monoethylenically unsaturated monomers, and the remaining amount of monoethylenically unsaturated monomers is metered in at a later time during the emulsion polymerization. The individual components can be metered in separately (spatially and temporally), or all or some of the components to be metered in pre-emulsified form. The initiators can, for example, be introduced in their entirety or partially metered in. The initiators are preferably metered in their entirety.

[0055] Preferably, initiators are also added after the monoethylenically unsaturated monomers have been completely metered in. This procedure is also referred to as a post-reaction. At the start of the post-reaction, the amount of monoethylenically unsaturated monomers that have not yet been polymerized is preferably 1 to 15% by weight, more preferably 1.5 to 10% by weight, particularly preferably 2 to 7% by weight and most preferably 3 to 6% by weight, based on the total weight of the monoethylenically unsaturated monomers. The amount of monoethylenically unsaturated monomers that have not yet been polymerized can be determined from the solids content of the dispersion present at the start of the post-reaction and the solids content theoretically to be expected upon complete polymerization. Gas chromatographic methods for quantifying the free monoethylenically unsaturated monomer are also suitable.The post-reaction is preferably carried out in a pressure reactor.

[0056] Preferably, after completion of the polymerization or any subsequent reaction, a further post-polymerization is carried out. During the post-polymerization, any remaining amounts of residual monomer are polymerized. At the start of a post-polymerization, the residual monomer content is generally lower than at the start of any subsequent reaction. The post-polymerization begins with an amount of as yet unpolymerized monoethylenically unsaturated monomers of preferably 0.5 to 10 wt. %, more preferably 1 to 7 wt. % and most preferably 2 to 5 wt. % based on the total weight of the monoethylenically unsaturated monomers. The amount of as yet unpolymerized monoethylenically unsaturated monomers can be determined from the solids content of the dispersion present at the start of the post-polymerization and the solids content theoretically to be expected upon completion of the reaction.Gas chromatographic methods for quantifying the free monoethylenically unsaturated monomer are also suitable. Unless otherwise stated, the post-polymerization is carried out using known methods, generally with redox catalyst-initiated post-polymerization. The post-polymerization can be carried out in the same reactor in which the polymerization was carried out. If the polymerization and / or any post-reaction was carried out in a pressure reactor, the post-polymerization is preferably carried out in a pressureless reactor. For this purpose, the polymerization mixture can be transferred from a pressure reactor to a pressureless reactor in a conventional manner.

[0057] The crosslinker monomers can, for example, be added wholly or partly during the main polymerization, wholly or partly at the start and / or during the post-reaction and / or wholly or partly at the start and / or during the post-polymerization. The main polymerization takes place up to the start of the post-polymerization or up to the start of any post-reaction. For example, the crosslinker monomers can be added wholly or, preferably, partly at a time before the post-reaction, in particular at a time at which the monoethylenically unsaturated monomers have been added to an extent of > 85% by weight, preferably > 90% by weight, more preferably > 93% by weight and particularly preferably > 95% by weight, based on the total weight of the monoethylenically unsaturated monomers. The complete addition of the crosslinker monomers at the start and / or during the post-reaction and / or at the start and / or during the post-polymerization is preferred.Particular preference is given to the complete addition of the crosslinker monomers at the beginning and / or during the post-reaction. Particular preference or even more preference is also given to the complete addition of the crosslinker monomers at the beginning and / or during the post-polymerization. The crosslinker monomers are preferably added in an amount of > 50% by weight, particularly preferably > 75% by weight and most preferably 100% by weight, based on the total weight of the crosslinker monomers, at the beginning and / or during the post-reaction and / or at the beginning and / or during the post-polymerization. Volatile compounds, such as residual monomer or impurities from initiator components or other raw materials, can also be removed from the aqueous dispersion by means of distillation or stripping. During stripping, volatile compounds are removed from the dispersions, optionally under reduced pressure, by passing through or over inert entraining gases, such as air, nitrogen or steam.

[0058] Following the polymerization of the crosslinking monomers, preferably no further monomers are added, preferably no further polymerization of ethylenically unsaturated monomers and / or no polymer-analogous reaction is carried out.

[0059] The copolymers in the form of aqueous dispersions have a solids content of preferably 30 to 75 wt.%, particularly preferably 50 to 60 wt.%.

[0060] Aqueous dispersions can be converted into copolymers in the form of water-redispersible powders by drying. For this purpose, drying aids are generally added to the aqueous dispersions, preferably in an amount of 0.5 to 30 wt. %, in particular 5 to 20 wt. %, based on the solids content of the aqueous dispersion. The total amount of drying aid and protective colloid before the drying process is preferably 1 to 30 wt. %, based on the solids content of the aqueous dispersion.

[0061] The aqueous dispersions can be dried, for example, by fluidized-bed drying, freeze-drying, or preferably spray-drying. Spray-drying can be carried out in conventional spray-drying systems, with atomization being effected by means of single-, dual-, or multi-component nozzles or with a rotating disk. The outlet temperature is generally selected in the range from 45°C to 120°C, preferably 60°C to 90°C, depending on the system, the Tg of the copolymers, and the desired degree of drying. The viscosity of the feed to be sprayed is adjusted via the solids content so that a value of < 500 mPas (Brookfield viscosity at 20 revolutions and 23°C), preferably < 250 mPas, is obtained. The solids content of the dispersion to be sprayed is preferably 30 to 75% by weight and particularly preferably 50 to 60% by weight.

[0062] In many cases, a content of up to 1.5% by weight of antifoam, based on the copolymers, has proven beneficial. Antifoam is preferably added during atomization.

[0063] To increase storage stability by improving blocking stability, particularly in the case of copolymer powders with a low glass transition temperature, the resulting powder can be treated, for example, with one or more antiblocking agents (anticaking agents). The antiblocking agents are preferably not added to the aqueous copolymer dispersions, i.e. preferably not before drying, but rather during or after drying, in particular during drying in the spray drying system. Preferred powders contain antiblocking agents, in particular 1 to 30% by weight, based on the total weight of polymeric constituents. Examples of antiblocking agents are Ca or Mg carbonate, talc, gypsum, silica, kaolins such as metakaolin, and silicates, preferably with particle sizes in the range from 10 nm to 10 pm.

[0064] The copolymers are generally suitable as binders for coatings or adhesives, in particular for paints, fibers, textiles, leather, paper, or carpets. Particular preference is given to using the copolymers as binders for bonding fiber materials, in particular for the production of textile fabrics such as nonwovens, knitted and woven fabrics, leather and furs, or carpets, or as binders for building coatings, in particular aqueous emulsion paints or powder paints. Furthermore, the copolymers are also suitable for use in construction chemical products.They can be used alone or in combination with conventional polymer dispersions or dispersion powders, if necessary in conjunction with hydraulically setting binders such as cements (Portland, aluminate, trass, granulated blast furnace slag, magnesia, phosphate cement), gypsum and water glass for the production of self-leveling compounds, construction adhesives, plasters, fillers, joint mortars, sealing slurries, external thermal insulation systems or paints, for example powder paints. Among construction adhesives, tile adhesives or full thermal insulation adhesives are preferred areas of application. Other preferred areas of application are self-leveling compounds; preferred self-leveling compounds are self-leveling floor fillers and screeds.

[0065] Surprisingly, the copolymers of the invention lead to advantageous mechanical properties in applications, particularly high tensile strength and elongation at break, and a favorable adhesion / cohesion balance. For example, textile fabrics bonded with copolymers of the invention exhibit high adhesive tensile strengths. Corresponding dye applications are distinguished by high abrasion resistance.

[0066] Advantageously, the process according to the invention also achieves the desired result for a wide variety of copolymers, such as copolymers with very different particle sizes, molecular weights, or viscosities—and this with measures that are inherently simple to implement in terms of process technology, through copolymerization of the crosslinking monomers according to the invention. The process according to the invention can be easily integrated into established polymerization processes without significant equipment expenditure and, above all, without lengthy development work, and is therefore easy to implement and can also be applied to a wide variety of processes for producing polymers with a wide variety of property profiles.What was particularly surprising here was that the process according to the invention offers all these advantages without significantly interfering with the viscosities, particle size distribution or the average particle sizes of the copolymers by copolymerizing crosslinking monomers, in particular without the otherwise occurring broadening of the particle size distribution and formation of coarse particles, which represents a particular challenge in the case of vinyl ester polymers.

[0067] The preferred embodiments of the method according to the invention contribute to achieving the object of the invention even better.

[0068] The following examples serve to further explain the invention.

[0069] Determination methods:

[0070] Determination of tensile elongation:

[0071] A polymer film with a thickness between 400 and 600 pm was produced using the respective polymer dispersion. After drying in vacuum for 24 h, the polymer films were tested for elongation at break and tensile strength according to DIN 53504 (S3a).

[0072] Particle size:

[0073] The determination was carried out using the light scattering method with a Coulter LS 1320. The D [4,3] values ​​and the corresponding CV value, which represents the ratio of standard deviation to the mean value of the volume distribution (q3) in percent, were output. The CV value is a measure of the width of the particle size distribution. The volume-weighted mean size is given in MV notation according to DIN ISO 9276-2. Degree of cross-linking:

[0074] A polymer film was prepared using the respective polymer dispersion as described above and dried under vacuum. A defined mass of the polymer film was then weighed into a Soxhlet extractor (Soxtec 8000, FOSS GmbH), a defined volume of 90 mL of ethyl acetate was added, and the resulting solution was heated under reflux for 6 h. After cooling and filtration, the proportion of dissolved polymer was determined from the clear solution. The degree of crosslinking is calculated as the ratio of undissolved polymer to weighed polymer in percent.

[0075] Determination of the glass transition temperature:

[0076] The glass transition temperature Tg of the polymers was determined in the conventional manner using differential scanning calorimetry (DSC). Measurements were taken in the temperature range between -70°C and 160°C under a continuous nitrogen flow (50 ml / min) in all sub-steps. The temporal resolution was one second. The measuring crucible was perforated prior to measurement. The measurement program is summarized in the table below.

[0077] Step Temperature Range Duration / Ramp

[0078] 1 25°C 5 min

[0079] 2 25-70°C -20 K / min

[0080] 3 -70°C 5 min

[0081] 4 -70-100°C 10 K / min

[0082] 5 100°C 15 min

[0083] 6 100-70°C -20 K / min

[0084] 7 -70°C 5 min

[0085] 8 -70-160°C 10 K / min

[0086] 9 160-70°C -20 K / min

[0087] 10 -70°C 5 min

[0088] 11 -70-160°C 10 K / min Measurement of the tuft pull-out force:

[0089] The tuft pull-out force was tested in accordance with ISO 4919 using a Zwick testing machine at 23°C and 50% relative humidity. The respective carpet was clamped into the attachment at the bottom of the measuring device, and a needle was threaded through a carpet loop. The force required to pull a loop out of the carpet was determined using ten different carpet loops. The average of the measurement results provided the dry tuft pull-out force.

[0090] The dry tuft pull-out strength is a measure of the quality of the tuft bond created by the primer and the wear characteristics of the carpet surface. Therefore, this strength should be as high as possible.

[0091] Measurement of separation strength:

[0092] The separation strength was determined analogously to DIN EN ISO 11857 ​​using a Zwick testing machine at 23 ° C and 50 % relative humidity. Three samples were produced by cutting strips 5 cm wide and 20 cm long from the respective carpet in the machine direction and then manually separating them along the narrow side over a length of 5 cm. Each separated sample was clamped in a Zwick testing machine and the secondary backing was separated from the carpet at a speed of 300 mm / min. The overall mean value from five samples was determined in accordance with DIN EN ISO 11857 ​​from the mean values ​​of the peak values ​​for each sample in the permissible measuring range. The first 25 % of each measurement curve was marked and not taken into account for the evaluation. The next 50 % of the diagram was divided into 5 equal sections and the respective peak value was determined from these.The peak values ​​were summarized for the mean, and the mean values ​​were summarized for the overall mean. The separation strength was given in Newtons [N]. Crosslinker monomers used:

[0093] Table 1: Crosslinker monomers:

[0094] Abbreviation Substance Name Supplier

[0095] TAG Triallylcyanurate Aldrich

[0096] ALMA Allyl Methacrylate Aldrich

[0097] Process VO for the preparation of dispersion A (without crosslinking monomer, not according to the invention): The following components were placed in a 5-liter pressure reactor flushed with nitrogen: [Introducer] 1.05 kg of deionized water, 348 g of a 20 wt.% aqueous solution of a polyvinyl alcohol with an average degree of hydrolysis of 88 mol% and a Höppler viscosity of 4 mPas (determined according to DIN 53015, at 20°C, in 4% aqueous solution),

[0098] 383 g of a 10 wt.% aqueous solution of a polyvinyl alcohol with an average degree of hydrolysis of 88 mol% and a Höppler viscosity of 13 mPas (determined according to DIN 53015, at 20°C, in 4% aqueous solution),

[0099] 31.5 g of a 40 wt.% aqueous solution of a fatty alcohol ethoxylate with an average degree of ethoxylation of 30 mol EO units, 2.01 kg vinyl acetate,

[0100] 0.5 g of a 10 wt.% aqueous ammonium iron sulfate solution.

[0101] The initial solution was adjusted to a pH of 3.9 with formic acid (98 wt%).

[0102] [Polymerization] While stirring (450 rpm), the initial charge was heated to 45°C and ethylene was injected up to a pressure of 30 bar. When the temperature of 45°C and a pressure of 30 bar were reached, the initiator feeds, consisting of an aqueous 3.0 wt. % potassium peroxodisulfate solution and an aqueous 5.0 wt. % sodium isoascorbate solution, were started at 20 g / h and 9 g / h respectively. 15 minutes after the start of the initiator feeds, the internal reactor temperature was raised to 75°C. When the internal reactor temperature reached 75°C, ethylene was added up to a target pressure of 67 bar, until a total amount of 490 g of ethylene had been metered. 2 hours after the start of the initiator feeds, 277 g of vinyl acetate were metered in within one hour.

[0103] [Post-reaction] After the end of the vinyl acetate dosing, the initiator dosing was continued for 60 minutes at 40 g / h and 20 g / h respectively, during which the pressure dropped to 20 bar.

[0104] [Post-polymerization]

[0105] The mixture was then cooled and transferred to a post-processing reactor, where it was post-polymerized by adding 20 g of tert-butyl hydroperoxide solution (TBHP, 10 wt.% in water) and 40 g of sodium isoascorbate solution (Na-i-AsAc, 5.0 wt.% in water). A polymer dispersion with the following properties was obtained: Solids content: 58.4 wt.% Brookfield viscosity: 2500 mPas (spindle 2, 20 rpm, 23°C), particle size: D[4,3] 1.38 pm, CV 56.9%, glass transition temperature: 5.7°C.

[0106] Process VO for the preparation of dispersion B (without crosslinking monomer, not according to the invention): The polymer dispersion B was prepared by modifying the process for the preparation of dispersion A and had the following properties: Glass transition temperature: 9.8 °C Solids content: 55.0 wt.-% Brookfield viscosity: 640 mPas (spindle 2, 20 rpm, 23°C) Particle size: D[4.3] 1.22 pm, CV 65.1% Process VI for the preparation of dispersions A-2, A-7 and A-8 as well as B1 to B-8 (according to the invention): Addition of the crosslinking monomers during the post-polymerization: Process VI was carried out analogously to process V0 for the preparation of dispersion A or dispersion B, with the difference that the post-polymerization was carried out as follows: To the polymerization batch obtained with initial charge, polymerization and post-reaction according to process V0 for the preparation of dispersion A or B, as indicated in Tables 2 to 5, with a solids content of 53.0% and a proportion of residual monomer (vinyl acetate) of 3.0 wt.%, based on the polymer present, was transferred to the post-processing reactor (pressureless vessel) for After polymerization at 50°C, a crosslinking monomer is added within 10 minutes according to the information in Tables 2 to 5.After the addition of the crosslinker monomer, 12 mL of TBHP (10%) and 6.6 mL of Na-i-AsAc (10%) were added over a period of 15 min while stirring, and post-polymerization was continued for a total of 40 min. The mixture was cooled to room temperature.

[0107] The properties of dispersions A-2, A-7 and A-8 as well as B1 to B-8 and the test results obtained with them are summarized in Tables 2 and 5.

[0108] Process VIA for the preparation of dispersion A-9 (according to the invention): Addition of the crosslinker monomers during the post-reaction: Process VIA was carried out analogously to process VO for the preparation of dispersion A, with the difference that the post-reaction was carried out as follows and the post-polymerization was modified as follows: At the beginning of the post-reaction in the pressure reactor, a crosslinker monomer according to the information in Table 2 was metered in over 10 minutes at 75°C to the polymerization batch obtained with initial charge and polymerization according to process VO for the preparation of dispersion A. At the same time, the initiator metered additions were continued for a further 60 minutes at 40 g / h and 20 g / h each, while the pressure dropped to approx. 20 bar. At the end of the post-reaction, the reaction mixture was let down in the post-processing reactor (pressureless vessel) and post-polymerization was carried out. 12 mL of TBHP (10%) and 6.5 mL of butyl acetate (10%) were added while stirring at 50°C.6 mL of Na-i-AsAc (10%) were added over 15 min and polymerized for a total of 40 min. The mixture was cooled to room temperature.

[0109] The properties of dispersion A-9 are summarized in Table 2 .

[0110] Process V2 for the preparation of the comparative dispersions VA-1, VA-3 and VA-4 (not according to the invention):

[0111] Submission of crosslinking monomers:

[0112] Process V2 was carried out analogously to process V0 for the preparation of dispersion A, with the difference that a crosslinking monomer was additionally added to the initial charge in accordance with the information in Table 2.

[0113] The properties of the dispersions VA-1, VA-3 and VA-4 are summarized in Table 2.

[0114] Process V3 for the preparation of the comparative dispersions VA-5 and VA-6 (not according to the invention): Dosage of crosslinking monomers:

[0115] Process V3 was carried out analogously to process V0 for the preparation of dispersion A, with the difference that during the polymerization a crosslinking monomer was metered in parallel with the vinyl acetate metering within one hour as specified in Table 2.

[0116] The properties of dispersions VA-5 and VA-6 are summarized in Table 2.

[0117] Discussion of the properties of the (comparative) dispersions in Table 2 :

[0118] The design of the polymerization process is crucial for improving the cohesive properties and cohesion-adhesion balance of the copolymers without significantly affecting the dispersion properties. The effect of the process on the resulting particle sizes and viscosities of the dispersions is shown in Table 2. Even small mass fractions of crosslinker monomer in the initial charge (process V2) have a significant impact on the average particle sizes and generally lead to a shift toward larger particles.

[0119] Similarly, this effect also occurs when crosslinking monomers are added during polymerization according to process V3.

[0120] An extreme increase in viscosity occurs, particularly when higher mass fractions of crosslinking monomers are added during polymerization (process V3).

[0121] According to the conventional processes V2 and V3 with complete initial introduction or dosing of the crosslinking monomers during polymerization, the cohesive properties and elongation at break of polymer films cannot be influenced without massively influencing the other polymer properties.

[0122] In contrast, the process according to the invention does not lead to a significant influence on the particle size or viscosity, but to an increase in the elongation at break.

[0123] According to the process according to the invention, even considerably larger mass fractions of crosslinking monomers can be introduced into the polymers without any significant change in viscosity or particle size.

[0124] Table 2 shows that by copolymerizing various crosslinker monomers according to the invention, the tear strength oB was considerably improved compared to the crosslinker monomer-free reference polymer dispersion A, the elongation at break sB was slightly reduced or remained within the desired range, and thus an overall advantageous cohesion-adhesion balance could be achieved, as shown with the inventive dispersions A-2 and A-7 compared to the reference polymer dispersion A. In contrast, the comparison dispersions A-1, A-4 and A-5 showed a sometimes considerable deterioration in the elongation at break sB and thus a deterioration in the cohesion-adhesion balance. The polymerization process is crucial for influencing the cohesive properties of copolymers.

[0125] The influence of the polymerization process on the copolymer properties, such as viscosity BF (20) or particle size distribution D[4,3], is particularly drastic, which is also reflected in the invariance parameter, as shown in Table 2 by the comparison of reference polymer dispersion A with the inventive dispersions A-2 and A-7, respectively, compared to the direct comparison dispersions A1 and A-6. The polymer properties of the remaining comparison dispersions A-3 to A-5 also differ dramatically from reference polymer dispersion A.

[0126] Table 2: Properties of dispersions prepared according to the

[0127] Procedures V0 to V3:

[0128] Networker Verfah _ BF(20) b > FG b) D[4,3] b > CV cB eB m

[0129] G o en womer: r , rn i r rianz _ %a) ren [mPa s] [%] [pm] r [% n n ] [MPa n ] r [%n i ]

[0130] A - V0 2500 58.4 1.38 0.0 56.9 4.99 443

[0131] VA-1 TAG: 0.01 V2 968 57.8 2.5 81.2 39.1 7.55 475

[0132] A-2 DAY: 0.40 VI 2560 58.6 1.15 16.7 21.6 6.67 413

[0133] VA-3 ALMA: 0.04 V2 948 58.1 3.58 159.4 32.8 8.86 454

[0134] VA-4 ALMA: 0.15 V2 334 57, 9 4.89 254.3 65.7 10.2 548.8

[0135] VA-5 ALMA: 0.10 V3 1200 58.3 1.62 17.4 53.2 9, 0 509.4

[0136] VA-6 ALMA: 0.20 V3 19800 58.7 2.94 113.0 48.3

[0137] A-7 ALMA: 0.20 VI 2095 58 1.24 10.1 42.8 7.55 464

[0138] A-9 ALMA: 0.10 VIA 2340 58.1 1.21 12.3 47.6 8.73 461 a) : % by weight of crosslinking monomer, based on the total mass of vinyl acetate; b) : abbreviations:

[0139] BF(20) : Brookfield viscosity determined at 23°C, at 20 rpm, with a dispersion solids content of 55%;

[0140] FG: fixed salary;

[0141] D[4,3] and CV : particle size distribution;

[0142] Invariance: particle size invariance; oB: tensile strength; eB: elongation at break.

[0143] All this shows that by copolymerizing crosslinker monomers according to the invention, polymer dispersions were obtained with properties that are virtually identical or at least in a similar range to those in the case of reference polymer dispersion A without crosslinker monomers, and the copolymers according to the invention also lead to an improved cohesion-adhesion balance (Table 2: Dispersions A-2 and A-7 compared to reference polymer dispersion A), whereas the non-inventive comparative polymer dispersions A1 and A-3 to A-6 all have completely different polymer properties than the reference polymer dispersion A.

[0144] Thus, the comparative polymer dispersions A-1 and A-3 to A-6 are not at all suitable for substituting the established reference polymer dispersion A in applications to improve cohesive properties - in contrast to the dispersions A-2 and A-7 according to the invention, which are ideally suited for this purpose.

[0145] Testing the elongation at break:

[0146] The tear strength (oB) of the polymer films could be increased by increasing the mass fraction of crosslinker monomer in the copolymers.

[0147] The degree of crosslinking of the copolymers could also be effectively adjusted via the mass fraction of crosslinking monomer.

[0148] Table 3: Tear strength oB and degree of crosslinking of copolymers with different crosslinker monomer content:

[0149] Ve rielze — Inva

[0150] Procedure BF(20) b) Excess Ver- eB b) CB b) monomer: riance b)

[0151] parts by weight31 ren [mPa s] wetting b) [%] [MPa]

[0152] [%]

[0153] A - V0 2510 0.0 1.00 443.1 4.99

[0154] A-7 ALMA: 0.2 VI 2095 16.5 1.15 464.0 7.55

[0155] A-8 ALMA: 0.4 VI 2465 1.8 1.33 518.7 9.52 a) parts by weight, based on the total mass of vinyl acetate b) : abbreviations:

[0156] BF(20) : Brookfield viscosity determined at 23°C, at 20 rpm, with a dispersion solids content of 55%;

[0157] Invariance : viscosity invariance;

[0158] Excess crosslinking: Excess factor of the degree of crosslinking (determined as specified in the general description); oB: Tensile strength; eB: Elongation at break. Testing the degree of crosslinking:

[0159] The process according to the invention makes it possible to efficiently and specifically vary the degree of crosslinking of the resulting copolymer over a wide range via the mass fraction of crosslinker monomer, as shown by way of example with the dispersions B1 to B-8 according to the invention prepared by process 1 compared to reference polymer dispersion B.

[0160] In application tests, the dispersions with a higher degree of crosslinking advantageously led to higher cohesion of the copolymers.

[0161] Table 4: Influence of the mass fraction of crosslinker monomer on the degree of crosslinking and particle size:

[0162] Dispersion crosslinker monomer: Process FG D[4,3] BET crosslinking

[0163] % by weight a| ren [%] [pm] [m 2 / g] degree [-]

[0164] B - V0 55.0 1.22 5.84 1.00

[0165] Bl ALMA: 0.2 VI 55.2 1.385 5.50 1.22

[0166] B-2 ALMA: 0.4 VI 55.1 1.386 5.49 1.24

[0167] B-3 ALMA: 0, 6 VI 55.1 1.4 5.48 1.29

[0168] B-4 ALMA: 1.0 VI 55.3 1, 442 5.42 1.20

[0169] B-5 DAY: 0.2 VI 55.0 1.268 6.01 1.25

[0170] B-6 DAY: 0.4 VI 55.1 1.266 6.04 1.26

[0171] B-7 DAY: 0.6 VI 54.9 1.529 5.31 1.29

[0172] B-8 TAG: 1.0 VI 55.0 1.434 5.39 1.25 a) : % by weight of crosslinking monomer, based on the total mass of polymer; conversion to mass fraction of crosslinking monomer, based on the total mass of vinyl acetate, by multiplying by a factor of 1.075; b) abbreviations:

[0173] FG: solids content; D[4,3] : particle size distribution;

[0174] BET: specific surface area;

[0175] Degree of crosslinking: expressed as the excess factor of the degree of crosslinking (determined as specified in the general description). Application of copolymer dispersions in carpet production:

[0176] Formulation 1 (Fl):

[0177] Carpet coating compositions were prepared based on the following recipe:

[0178] 100 parts by weight of the respective dispersion as indicated in Table 5 (polymer dry),

[0179] 800 parts by weight of chalk (Carbocia 80, Carbocia) (filler),

[0180] 1.6 parts by weight of dispersant (Mateo DR 35, Mateo),

[0181] 0.7 parts by weight of foaming agent (sodium lauryl sulfate).

[0182] The parts by weight refer to the dry weight of the respective carpet coating composition.

[0183] Additional water was added in an amount to result in carpet coating compositions with a solids content of 70.0 wt.%.

[0184] To prepare the carpet coating compositions, the water and the respective dispersion or dispersion mixture were added and the filler and then the foaming agent were added while stirring.

[0185] The carpet coating compositions had a solids content of 70.0 wt% and a filler content of 800 wt%.

[0186] Subsequently, a final viscosity of 1000 mPas was adjusted by adding a thickener (acrylate thickener Mateo TR 10, Mateo) (measurement with Brookfield RV measuring device with spindle 4, 20 rpm, at 25°C).

[0187] Formulation 2 (F2):

[0188] As formulation Fl, but with 300 parts by weight of chalk (Carbocia 80, Carbocia).

[0189] Additional water was added in an amount to result in carpet coating compositions with a solids content of 78.0 wt.%.

[0190] By adding a thickener (acrylate thickener Mateo TR 10, Mateo), a final viscosity of 1000 mPas was achieved (measured with a Brookfield RV meter with spindle 4, 20 rpm, at 25°C). Carpet production

[0191] The respective carpet coating composition described above was foamed for 3 minutes using a food processor, achieving foam liter weights of 490 - 510 g / L. As a precoat, 87 g of the respective foamed carpet coating composition was evenly distributed over a 38 cm x 33 cm tufted carpet (loop pile tufted carpet: 100% polypropylene, hereinafter referred to as PP; 550 g / m 2 Pile weight; quality Helsinki; manufacturer: Edel).

[0192] Subsequently, 78 g of a foamed carpet coating composition F2 (500 g / L) was applied as a secondary coating and evenly distributed. A textile backing (polypropylene fabric, Action Back) was then applied and worked in twice with a 1.6 kg roller without applying pressure. It was dried in an oven at 130°C for 20 minutes.

[0193] The tuft pull-out force and separation strength of the resulting carpets were determined. The test results are summarized in Table 5.

[0194] Table 5: Results of the application testing of Disp. B (Tg 9.8 °C):

[0195] Example: Dispersion Crosslinker Separation strength Knob pull-out force [wt.%]* (dry) (dry)

[0196] [N] [N]

[0197] El B - 26.5 34.16

[0198] Dl B-4 1.0 39.1 37.58

[0199] D-2 B-8 1.0 35.8 33.89

[0200] % by weight of crosslinker monomer, based on the total mass of polymer; conversion to mass fraction of crosslinker monomer, based on the total mass of vinyl acetate, by multiplying by a factor of 1.075.

Claims

Patent claims: 1 . Process for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders by radically initiated emulsion polymerization of one or more monoethylenically unsaturated monomers and one or more polyethylenically unsaturated monomers and optionally subsequent drying, characterized in that > 85 wt . % of the monoethylenically unsaturated monomers are polymerized and then one or more polyethylenically unsaturated monomers are added, the information in wt . % relating to the total weight of the monoethylenically unsaturated monomers.

2. A process for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders according to claim 1, characterized in that one or more polyethylenically unsaturated monomers carry 2 to 6 ethylenically unsaturated groups and at least one or more functional groups selected from the group comprising ester, amide, ether, carbonate, cyanurate or thioether groups. 3 . Process for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders according to claim 1 or 2, characterized in that one or more polyethylenically unsaturated monomers are selected from the group comprising allyl methacrylate, allyl acrylate, vinyl methacrylate, vinyl acrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, propylene glycol diacrylate, 1,3-glycerol dimethacrylate, 1,1,1-trimethylolethane diacrylate, 1,1,1-trimethylpropane dimethacrylate, methylenebisacrylamide, methylenebismethacrylamide, diallyl maleate, diallyl fumarate, Diallyl litaconate, diallyl malonate, diallyl phthalate, vinyl crotonate, divinyl adipate, divinyl benzene, divinyl ether, ethylene glycol divinyl ether, diallyl carbonate, Trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, triallyl cyanurate, triallyl isocyanurate, triallyl citrate, triallyl laconitate and sorbitol pentamethacrylate.

4. A process for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 3, characterized in that one or more monoethylenically unsaturated monomers are selected from the group comprising vinyl esters, (meth)acrylic acid esters, vinyl aromatics, olefins and vinyl halides.

5. A process for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 4, characterized in that the polyethylenically unsaturated monomers are used in an amount of 0.01 to 5% by weight, based on the total weight of the monoethylenically unsaturated monomers. 6 . A process for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 5, characterized in that > 93 wt . - % , based on the total weight of the monoethylenically unsaturated monomers, of the monoethylenically unsaturated monomers are polymerized and then one or more polyethylenically unsaturated monomers are added for the first time.

7. A process for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 6, characterized in that the polyethylenically unsaturated monomers are added to an amount of > 70 wt. % based on the total weight of the crosslinking monomers at a time when the monoethylenically unsaturated monomers have been polymerized to an amount of > 90 wt. % based on the total weight of the monoethylenically unsaturated monomers. 8 . A process for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 7, characterized in that after complete metering of the monoethylenically unsaturated monomers, initiators are added and the complete or partial addition of the polyethylenically unsaturated monomers takes place. 9 . A process for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 8, characterized in that after completion of the polymerization, a post-polymerization is carried out and at the beginning and / or during the post-polymerization, the polyethylenically unsaturated monomers are added in full or in part.

10. A process for the preparation of copolymers in the form of aqueous dispersions or water-redispersible powders according to claims 1 to 9, characterized in that the polyethylenically unsaturated monomers are added in an amount of > 50 wt. % based on the total weight of the polyethylenically unsaturated monomers after complete metering of the monoethylenically unsaturated monomers, in particular at the beginning and / or during the post-polymerization.

11. Copolymers in the form of aqueous dispersions or water-redispersible powders obtainable according to claims 1 to 10.

12. Copolymers in the form of aqueous dispersions or water-redispersible powders according to claim 11, characterized in that the copolymers have a particle size invariance of < 30%, wherein the particle size invariance is the absolute value of the quotient of the particle size of the copolymer according to claim 11 and the particle size of a reference polymer minus 1 in percent, wherein the reference polymer is produced identically to the copolymer according to claim 11, with the only difference that no polyethylenically unsaturated monomer is polymerized into the reference polymer, wherein the particle size is determined using the Beckmann Coulter® LS 13320 measuring device.

13. Use of the copolymers in the form of aqueous dispersions or water-redispersible powders from claims 11 to 12 as binders for coating materials or adhesives, in particular for paints, textiles, paper or carpets. 14 . Use of the copolymers in the form of aqueous dispersions or water-redispersible powders from claims 11 to 12 in leveling compounds, construction adhesives, tile adhesives, full thermal insulation adhesives, plasters, fillers, joint mortars, sealing slurries or paints .

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